Update on K2-18b

There might not be hycean worlds, that is worlds with hydrogen rich atmosphere over liquid ocean.

A recent study could explain the spectral signature of another potential hycean world, TOI 270d, by an atmosphere over a magma ocean, an environment not conductive to our kind of oceanic of organic life. Bummer.

But a lava world with boiling atmosphere is interesting to me – those were the conditions of early Earth during Hadean Eon, just after forming. Once the lava cooled enough to form a crust and tolerate liquid water, we got our early ocean, either from meteors or from inside the mantle.

Earth was small enough to cool soon, now only the ferrous core is molten, maintaining the Earth’s magnetic field and volcanism, both essential for life. Magnetic field shields us from space radiation whereas volcanism recycles back to surface nutrients, gases and water that would otherwise have sedimented or seeped into ground.

The reason we have oceans in the surface is volcanism, which pushes water towards the surface. Yet, lithosphere contains water, maybe multiple times the amount in world’s oceans.

So, while a hycean world is not proven, it is not impossible, either. I wonder if maybe, once a large lava world with lots of hydrogen and water vapor cools down enough to have an ocean, a hycean world arises.